Three-dimensional memory device with source structure and methods for forming the same

ABSTRACT

Embodiments of structure and methods for forming a three-dimensional (3D) memory device are provided. In an example, a 3D memory device includes a memory stack, a plurality of channel structures, and a source structure. The memory stack is over a substrate and includes interleaved a plurality of conductor layers and a plurality of insulating layers. The source structure includes a plurality of source contacts, and two adjacent ones of the plurality of source contacts are conductively connected to one another by a connection layer. A pair of first portions of the connection layer are over the two adjacent ones of the plurality of source contacts and a second portion of the connection layer being between the two adjacent ones of the plurality of source contacts. Top surfaces of the pair of first portions of the connection are coplanar with a top surface of the second portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of International Application No.PCT/CN2019/100350, filed on Aug. 13, 2019, entitled “THREE-DIMENSIONALMEMORY DEVICE WITH SOURCE STRUCTURE AND METHODS FOR FORMING THE SAME,”which is hereby incorporated by reference in its entirety. Thisapplication is also related to co-pending U.S. application Ser. No.______, Attorney Docketing No.: 10018-01-0060-US, filed on even date,entitled “THREE-DIMENSIONAL MEMORY DEVICE WITH SOURCE STRUCTURE ANDMETHODS FOR FORMING THE SAME,” and co-pending U.S. application Ser. No.______, Attorney Docketing No.: 10018-01-0061-US, filed on even date,entitled “THREE-DIMENSIONAL MEMORY DEVICE WITH SOURCE STRUCTURE ANDMETHODS FOR FORMING THE SAME,” all of which are hereby incorporated byreference in their entireties.

BACKGROUND

Embodiments of the present disclosure relate to three-dimensional (3D)memory devices having source structures of reduced resistance, andmethods for forming the 3D memory devices.

Planar memory cells are scaled to smaller sizes by improving processtechnology, circuit design, programming algorithm, and fabricationprocess. However, as feature sizes of the memory cells approach a lowerlimit, planar process and fabrication techniques become challenging andcostly. As a result, memory density for planar memory cells approachesan upper limit.

A 3D memory architecture can address the density limitation in planarmemory cells. 3D memory architecture includes a memory array andperipheral devices for controlling signals to and from the memory array.

SUMMARY

Embodiments of 3D memory devices and methods for forming the 3D memorydevices are provided.

In one example, a 3D memory device includes a memory stack, a pluralityof channel structures, and a source structure. The memory stack is overa substrate and includes interleaved a plurality of conductor layers anda plurality of insulating layers. The plurality of channel structuresextend vertically in the memory stack. The source structure extend inthe memory stack. The source structure includes a plurality of sourcecontacts each in a respective insulating structure, and two adjacentones of the plurality of source contacts are conductively connected toone another by a connection layer. A pair of first portions of theconnection layer are over the two adjacent ones of the plurality ofsource contacts and a second portion of the connection layer beingbetween the two adjacent ones of the plurality of source contacts. Topsurfaces of the pair of first portions of the connection are coplanarwith a top surface of the second portion of the connection layer.

In another example, a 3D memory device includes a memory stack, aplurality channel structures, and a plurality of source structures. Thememory stack is over a substrate. The memory stack includes interleaveda plurality of conductor layers and a plurality of insulating layers.The plurality of channel structures extend vertically in the memorystack. The plurality of source structures extend in parallel along alateral direction in the memory stack. The plurality of sourcestructures each includes a plurality of source contacts each in arespective insulating structure, a plurality of support structures eachin contact with adjacent insulating structures along the lateraldirection, and a connection layer conductively connected to at least twoadjacent ones of the plurality of source contacts. The connection layerinclude at least two first portions over the at least two adjacent onesof the plurality of source contacts and at least one second portionbetween the at least two adjacent ones of the plurality of sourcecontacts Top surfaces of the at least two first portions and the atleast one second portion of the connection layer are coplanar with oneanother.

In a further example, a method for forming a 3D memory device includesthe following operations. A cut structure is first formed in a stackstructure. The stack structure includes interleaved a plurality ofinitial sacrificial layers and a plurality of initial insulating layers.A patterned cap material layer is formed over the stack structure. Thepatterned cap material layer includes an opening over the cut structure.Portions of the stack structure and the patterned cap material layeradjacent to the opening are removed to form a slit structure and aninitial support structure. The initial support structure divide the slitstructure into a plurality of slit openings. A plurality of conductorportions are formed through the plurality of slit openings to form asupport structure. A source contact is formed in each of the pluralityof slit openings. A connection layer is formed over the source contactin each of the plurality of slit openings and over the supportstructure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate embodiments of the present disclosureand, together with the description, further serve to explain theprinciples of the present disclosure and to enable a person skilled inthe pertinent art to make and use the present disclosure.

FIG. 1A illustrates a plan view of an exemplary 3D memory device havingsource structures of reduced resistance, according to some embodimentsof the present disclosure.

FIG. 1B illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 1A along the C-D direction, according to someembodiments of the present disclosure.

FIG. 1C illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 1A along the A-B direction, according to someembodiments of the present disclosure.

FIG. 2A illustrates a plan view of an exemplary 3D memory device at onestage of a fabrication process, according to some embodiments of thepresent disclosure.

FIG. 2B illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 2A along the C-D direction, according to someembodiments of the present disclosure.

FIG. 3A illustrates a plan view of the exemplary 3D memory device atanother stage of the fabrication process, according to some embodimentsof the present disclosure.

FIG. 3B illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 3A along the C-D direction, according to someembodiments of the present disclosure.

FIG. 3C illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 3A along the A-B direction, according to someembodiments of the present disclosure.

FIG. 4A illustrates a plan view of the exemplary 3D memory device atanother stage of the fabrication process, according to some embodimentsof the present disclosure.

FIG. 4B illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 4A along the C-D direction, according to someembodiments of the present disclosure.

FIG. 5A illustrates a plan view of the exemplary 3D memory device atanother stage of the fabrication process, according to some embodimentsof the present disclosure.

FIG. 5B illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 5A along the C-D direction, according to someembodiments of the present disclosure.

FIG. 6A illustrates a plan view of the exemplary 3D memory device atanother stage of the fabrication process, according to some embodimentsof the present disclosure.

FIG. 6B illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 6A along the C-D direction, according to someembodiments of the present disclosure.

FIG. 6C illustrates a cross-sectional view of the 3D memory deviceillustrated in FIG. 6A along the A-B direction, according to someembodiments of the present disclosure.

FIG. 7A illustrates a plan view of an exemplary pattern set for formingvarious structures in a fabrication process for forming a 3D memorydevice, according to some embodiments of the present disclosure.

FIG. 7B illustrates an enlarged view of a portion of the pattern setshown in FIG. 7A, according to some embodiments of the presentdisclosure.

FIG. 8 illustrates a cross-sectional view of an existing 3D memorydevice with deformed gate line slits (GLSs).

FIG. 9 illustrates a flowchart of an exemplary fabrication process forforming a 3D memory device having source structures of reducedresistance, according to some embodiments of the present disclosure.

Embodiments of the present disclosure will be described with referenceto the accompanying drawings.

DETAILED DESCRIPTION

Although specific configurations and arrangements are discussed, thisshould be understood that this is done for illustrative purposes only. Aperson skilled in the pertinent art will recognize that otherconfigurations and arrangements can be used without departing from thespirit and scope of the present disclosure. It will be apparent to aperson skilled in the pertinent art that the present disclosure can alsobe employed in a variety of other applications.

It is noted that references in the specification to “one embodiment,”“an embodiment,” “an example embodiment,” “some embodiments,” etc.,indicate that the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases do not necessarily refer to the same embodiment. Further,when a particular feature, structure or characteristic is described inconnection with an embodiment, it would be within the knowledge of aperson skilled in the pertinent art to affect such feature, structure orcharacteristic in connection with other embodiments whether or notexplicitly described.

In general, terminology may be understood at least in part from usage incontext. For example, the term “one or more” as used herein, dependingat least in part upon context, may be used to describe any feature,structure, or characteristic in a singular sense or may be used todescribe combinations of features, structures or characteristics in aplural sense. Similarly, terms, such as “a,” “an,” or “the,” again, maybe understood to convey a singular usage or to convey a plural usage,depending at least in part upon context. In addition, the term “basedon” may be understood as not necessarily intended to convey an exclusiveset of factors and may, instead, allow for existence of additionalfactors not necessarily expressly described, again, depending at leastin part on context.

As used herein, the term “nominal/nominally” refers to a desired, ortarget, value of a characteristic or parameter for a component or aprocess operation, set during the design phase of a product or aprocess, together with a range of values above and/or below the desiredvalue. The range of values can be due to slight variations inmanufacturing processes or tolerances. As used herein, the term “about”indicates the value of a given quantity that can vary based on aparticular technology node associated with the subject semiconductordevice. Based on the particular technology node, the term “about” canindicate a value of a given quantity that varies within, for example,10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

As used herein, a staircase structure refers to a set of surfaces thatinclude at least two horizontal surfaces (e.g., along x-y plane) and atleast two (e.g., first and second) vertical surfaces (e.g., alongz-axis) such that each horizontal surface is adjoined to a firstvertical surface that extends upward from a first edge of the horizontalsurface, and is adjoined to a second vertical surface that extendsdownward from a second edge of the horizontal surface. A “step” or“staircase” refers to a vertical shift in the height of a set ofadjoined surfaces. In the present disclosure, the term “staircase” andthe term “step” refer to one level of a staircase structure and are usedinterchangeably. In the present disclosure, a horizontal direction canrefer to a direction (e.g., the x-axis or the y-axis) parallel with thetop surface of the substrate (e.g., the substrate that provides thefabrication platform for formation of structures over it), and avertical direction can refer to a direction (e.g., the z-axis)perpendicular to the top surface of the structure.

NAND flash memory devices, widely used in various electronic produces,are non-volatile, light-weighted, of low power consumption and goodperformance. Currently, planar NAND flash memory devices have reachedits storage limit. To further increase the storage capacity and reducethe storage cost per bit, 3D NAND memory devices have been proposed. Anexisting 3D NAND memory device often includes a plurality of memoryblocks. Adjacent memory blocks are often separated by a GLS, in which anarray common source (ACS) is formed. In the fabrication method to formthe existing 3D NAND memory device, due to an increased number of levels(or conductor/insulator pairs), the etching process to form GLSs becomechallenging. For example, the GLSs can be more susceptible todeformation, e.g., fluctuation of feature size, causing memory blocksneighboring the GLSs to deform or even collapse. The performance of the3D NAND memory device can be affected.

FIG. 8 illustrates an existing 3D memory device 800 with deformed GLSsand a deformed memory block. As shown in FIG. 8, a memory stack 811 isformed over a substrate 802. A plurality of GLS, e.g., 806-1 and 806-2,extend through memory stack 811 to expose substrate 802. A plurality ofchannel structures 804 are arranged in a memory block between GLSs 806-1and 806-2. Due to deformation, a lateral dimension, e.g., diameter D, ofGLS (e.g., 806-1 or 806-2) varies along the vertical direction (e.g.,the z-direction), causing the memory block and channel structures 804,to move from their desired position/orientation. These deformations canlead to photolithography misalignment and electrical leakage insubsequent fabrication processes that form ACSs in the GLSs.

The present disclosure provides 3D memory devices (e.g., 3D NAND memorydevices) having source structures with reduced resistance, and methodsfor forming the 3D memory devices. A 3D memory device employs one ormore support structures that divide a slit structure into a plurality ofslit openings, in which source contacts are formed. The supportstructures are each in contact with adjacent memory blocks, providingsupport to the entire structure of the 3D memory device during theformation of conductor layers/portions and source contacts. The 3Dmemory device is then less susceptible to deformation or damages duringthe fabrication process.

In the 3D memory device, at least two adjacent source contacts are incontact with and conductively connected to one another through aconnection layer, which includes a conductive material such as tungsten.One or more pairs of adjacent source contacts in a source structure canbe in contact with and conductively connected together by the connectionlayer. Instead of applying a source voltage on each of the plurality ofsource contacts using a respective contact plug, the source voltage isapplied on the source contacts (e.g., the source contacts that are incontact with connection layer) through the connection layer(s), reducingor eliminating the use of contact plugs. The resistance of the sourcestructure can be reduced. The contact area between the connection layerand a source contact can be sufficiently large to further reduce theresistance of the source structure. In some embodiments, the connectionlayer is in contact with and conductively connected to all the sourcecontacts in a source structure, further reducing the resistance of thesource structure. The connection layer can be formed in a singledeposition process, simplifying the fabrication process.

FIG. 1A illustrates a plan view of an exemplary 3D memory device 100,according to some embodiments. FIG. 1B illustrates a cross-sectionalview of the 3D memory device 100 shown in FIG. 1A along the C-Ddirection. FIG. 1C illustrates a cross-sectional view of the 3D memorydevice 100 shown in FIG. 1A along the A-B direction. As shown in FIG.1A, 3D memory device 100 may include a core region in which one or more,e.g., a pair of, source regions 22 extend along the x-direction. Asource structure may be formed in each source region 22. One or moreblock regions 21, in which a plurality of memory cells are formed, maybe between the pair of source regions 22. A memory block may be formedin each block region 21.

As shown in FIGS. 1A-1C, 3D memory device 100 may include a substrate102, and a stack structure 111 over substrate 102. In block regions 21,stack structure 111 may include a plurality of conductor layers 123 anda plurality of insulating layers 124 interleaved over substrate 102. Inblock regions 21, stack structure 111 may also include a plurality ofchannel structures 110 extending through stack structure 111 intosubstrate 102 along a vertical direction (e.g., the z-direction). Eachchannel structure 110 may include an epitaxial portion at a bottomportion, a drain structure at a top portion, and a semiconductor channelbetween the epitaxial portion and the drain structure. The semiconductorchannel may include a memory film, a semiconductor layer, and adielectric core. The epitaxial portion may be in contact with andconductively connected to substrate 102. The semiconductor channel maybe in contact with and conductively connected to the drain structure andthe epitaxial portion. A plurality of memory cells may be formed by thesemiconductor channels and control conductor layers.

A source structure may be formed in source region 22 to extend along thex-direction. The source structure may include a plurality of sourcecontacts 104 each in a respective insulating structure (not shown).Source contacts 104 and the respective insulating structures formed inone source region 22 (e.g., within the same source structure) may bealigned along the x-direction. The source structures, each in contactwith and conductively connected to substrate 102, may extend verticallythrough stack structure 111. A source voltage can be applied to thememory cells through the source structure and substrate 102. 3D memorydevice 100 may include one or more support structures 220 aligned alongthe x-direction and dividing a source structure into the plurality ofsource contacts 104 each in the respective insulating structure. In someembodiments, support structure 220 includes a cut structure 114 and aportion stack 221 between cut structure 114 and substrate 102. Portionstack 221 may include interleaved a plurality of conductor portions 223and insulating portions 224 over substrate 102. Each support structure220 may be in contact with adjacent memory blocks (or block regions 21)along the y-direction, and in contact with adjacent insulatingstructures of the respective source structure along the x-direction.Support structure 220 may provide support to 3D memory device 100 duringthe formation of the source structures and conductor layers 123. 3Dmemory device 100 may further include a connection layer 108 in contactwith and conductively connected to at least two adjacent source contacts104, and a dielectric cap layer 115 surrounding connection layer 108along the x-direction. Dielectric cap layer 115 may insulate connectionlayer 108 from other structures or devices in the x-y plane. Contactplugs (not shown) for conductively applying a source voltage can beformed at desired location(s) on connection layer 108. In someembodiments, dielectric cap layer 115 also covers at least a portion ofblock region 21. In some embodiments, dielectric cap layer 115 coversall channel structures 110 in block region 21. Contact plugs (not shown)for conductively applying a drain voltage can be formed extendingthrough dielectric cap layer 115 and form contact with channelstructures 110. For ease of illustration, coverage of dielectric caplayer 115 in block region 21 is not depicted. In some embodiments,connection layer 108 is over and in contact with all the source contacts104 in a source structure so that source voltage can be applied on allthe source contacts 104 of the source structure through connection layer108. The resistance of the source structure can be reduced compared toapplying the source voltage onto each source contact 104 using arespective contact plug. Details of each structure illustrated in FIGS.1A-1C are described below.

Substrate 102 can include silicon (e.g., single crystalline silicon),silicon germanium (SiGe), gallium arsenide (GaAs), germanium (Ge),silicon on insulator (SOD, germanium on insulator (GOI), or any othersuitable materials. In some embodiments, substrate 102 is a thinnedsubstrate (e.g., a semiconductor layer), which was thinned by grinding,etching, chemical mechanical polishing (CMP), or any combinationthereof. In some embodiments, substrate 102 includes silicon.

Channel structures 110 may form an array and may each extend verticallyabove substrate 102. Channel structure 110 may extend through aplurality of pairs each including a conductor layer 123 and aninsulating layer 124 (referred to herein as “conductor/insulating layerpairs”). At least on one side along a horizontal direction (e.g.,x-direction and/or y-direction), stack structure 111 can include astaircase structure (not shown). The number of the conductor/insulatinglayer pairs in stack structure 111 (e.g., 32, 64, 96, or 128) determinesthe number of memory cells in 3D memory device 100. In some embodiments,conductor layers 123 and insulating layers 124 in stack structure 111are alternatingly arranged along the vertical direction in block regions21. Conductor layers 123 can include conductive materials including, butnot limited to, tungsten (W), cobalt (Co), copper (Cu), aluminum (Al),polysilicon, doped silicon, silicides, or any combination thereof.Insulating layers 124 can include dielectric materials including, butnot limited to, silicon oxide, silicon nitride, silicon oxynitride, orany combination thereof. In some embodiments, conductor layers 123 mayinclude a top conductor layer having a plurality of top select conductorlayers, and a bottom conductor layer having a plurality of bottom selectconductor layers. The top select conductor layers may function as thetop select gate electrodes, and the bottom select conductor layers mayfunction as the bottom select gate electrodes. Conductor layers 123between the top and bottom conductor layers may function as select gateelectrodes and form memory cells with intersecting channel structures110. Top select gate electrodes and bottom select gate electrodes canrespectively be applied with desired voltages to select a desired memoryblock/finger/page.

Channel structure 110 can include a semiconductor channel extendingvertically through stack structure 111. The semiconductor channel caninclude a channel hole filled with a channel-forming structure, e.g.,semiconductor materials (e.g., as a semiconductor layer) and dielectricmaterials (e.g., as a memory film). In some embodiments, thesemiconductor layer includes silicon, such as amorphous silicon,polysilicon, or single crystalline silicon. In some embodiments, thememory film is a composite layer including a tunneling layer, a memorylayer (also known as a “charge trap layer”), and a blocking layer. Theremaining space of the channel hole of semiconductor channel can bepartially or fully filled with a dielectric core including dielectricmaterials, such as silicon oxide. The semiconductor channel can have acylinder shape (e.g., a pillar shape). The dielectric core,semiconductor layer, the tunneling layer, the memory layer, and theblocking layer are arranged radially from the center toward the outersurface of the pillar in this order, according to some embodiments. Thetunneling layer can include silicon oxide, silicon oxynitride, or anycombination thereof. The memory layer can include silicon nitride,silicon oxynitride, silicon, or any combination thereof. The blockinglayer can include silicon oxide, silicon oxynitride, high dielectricconstant (high-k) dielectrics, or any combination thereof. In oneexample, the memory layer can include a composite layer of siliconoxide/silicon oxynitride (or silicon nitride)/silicon oxide (ONO).

In some embodiments, channel structure 110 further includes an epitaxialportion (e.g., a semiconductor plug) in the lower portion (e.g., at thelower end of bottom) of channel structure 110. As used herein, the“upper end” of a component (e.g., channel structure 110) is the endfarther away from substrate 102 in the vertical direction, and the“lower end” of the component (e.g., channel structure 110) is the endcloser to substrate 102 in the vertical direction when substrate 102 ispositioned in the lowest plane of 3D memory device 100. The epitaxialportion can include a semiconductor material, such as silicon, which isepitaxially grown from substrate 102 in any suitable directions. It isunderstood that in some embodiments, the epitaxial portion includessingle crystalline silicon, the same material as substrate 102. In otherwords, the epitaxial portion can include an epitaxially-grownsemiconductor layer grown from substrate 102. The epitaxial portion canalso include a different material than substrate 102. In someembodiments, the epitaxial portion includes at least one of silicon,germanium, and silicon germanium. In some embodiments, part of theepitaxial portion is above the top surface of substrate 102 and incontact with semiconductor channel. The epitaxial portion may beconductively connected to semiconductor channel. In some embodiments, atop surface of the epitaxial portion is located between a top surfaceand a bottom surface of a bottom insulating layer 124 (e.g., theinsulating layer at the bottom of stack structure 111).

In some embodiments, channel structure 110 further includes a drainstructure (e.g., channel plug) in the upper portion (e.g., at the upperend) of channel structure 110. The drain structure can be in contactwith the upper end of a semiconductor channel and may be conductivelyconnected to the semiconductor channel. The drain structure can includesemiconductor materials (e.g., polysilicon) or conductive materials(e.g., metals). In some embodiments, the drain structure includes anopening filled with Ti/TiN or Ta/TaN as an adhesion layer and tungstenas a conductor material. By covering the upper end of semiconductorchannel during the fabrication of 3D memory device 100, the drainstructure can function as an etch stop layer to prevent etching ofdielectrics filled in the semiconductor channel, such as silicon oxideand silicon nitride.

As shown in FIGS. 1A-1C, a source structure can be formed in sourceregion 22. The source structure, aligned along the x-direction, mayinclude a plurality of source contacts 104 each in a respectiveinsulating structure (not shown). Each source contact 104 may be incontact with and conductively connected to substrate 102. The insulatingstructure may insulate the respective source contact 104 from conductorlayers 123 in adjacent block regions 21. In some embodiments, sourcecontact 104 includes at least one of polysilicon, aluminum, cobalt,copper, and silicides. The insulating structure can include a suitabledielectric material, such as one or more of silicon oxide, siliconnitride, and silicon oxynitride.

One or more support structures 220 may be distributed in a respectivesource structure along the x-direction. In some embodiments, the supportstructures 220 divides the respective source structure into theplurality of source contacts 104, each in the respective insulatingstructures (e.g., the insulating structure surrounding source contact104). In some embodiments, each source contact 104 and the respectiveinsulating structure is separated from another source contact 104 andanother insulating structure by a support structure 220. Supportstructure 220, in contact with portions of stack structure 111 inadjacent block regions 21, may include cut structure 114 and portionstack 221 under cut structure 114. In some embodiments, portion stack221 includes interleaved a plurality of conductor portions 223 and aplurality of insulating portions 224. In some embodiments, a width ofcut structure 114 along the y-direction may be greater than, equal to,or less than a total width of source contact 104 and the respectiveinsulating structure (e.g., a width of the source structure). In someembodiments, the width of cut structure 114 along the y-direction isequal to or less than the width of the source structure. In someembodiments, a thickness t of cut structure 114 along the z-directionmay be between two conductor/insulating pairs (i.e., interleaved twoconductor layers 123 and two insulating layers 124) and fourconductor/insulating pairs (i.e., interleaved four conductor layers 123and four insulating layers 124). Cut structure 114 may be in contactwith a plurality of interleaved conductor layers 123 and insulatinglayers 124 in adjacent block regions 21. Conductor portions 223 andinsulating portions 224 may respectively be in contact withcorresponding conductor layers 123 and insulating layers 124 of the samelevel in adjacent block regions 21. In some embodiments, a top surfaceof a source contact 104 is lower than a top surface of support structure220 along the z-direction. In some embodiments, of the same sourcestructure, top surfaces of all source contacts 104 are lower than topsurfaces of all support structures 220. In some embodiments, supportstructure 220 includes a spacer layer 225 under cut structure 114 andsurrounding portion stack 221. Spacer layer 225 may provide furtherinsulation between portion stack 221 and adjacent source contacts 104.

Each source structure may further include connection layer 108 over andin contact with at least two adjacent source contacts 104. For example,connection layer 108 may be in contact with and conductively connectedto one or more pairs of adjacent source contacts 104. Connection layer108 may be conductively connected to the source contacts 104 with whichit's in contact. In some embodiments, connection layer 108 partially orfully covers source contacts 104 to which it's in contact with. In someembodiments, connection layer 108 partially covers source contacts 104to which it's in contact with along the y-direction. As shown in FIGS.1A-1C, connection layer 108 may be over two adjacent source contacts 104and the support structure 220 between the two adjacent source contacts104. For example, connection layer 108 may partially or fully cover twoadjacent source contacts 104 and the support structure 220 between thetwo adjacent source contacts 104. The portion of connection layer 108 incontact with and conductively connected to source contact 104 may bereferred to as a first portion 108-1 of connection layer 108. Theportion of connection layer 108 in contact with support structure 220may be referred to as a second portion 108-2 of connection layer 108. Insome embodiments, second portion 108-2 of connection layer 108 may be incontact with and conductively connected to a pair of first portions108-1, e.g., adjacent first portions 108-1 on both sides of secondportion 108-2 along the x-direction. In some embodiments, connectionlayer 108 may include a plurality of first portions 108-1 and aplurality of second portions 108-2 in contact with and conductivelyconnected to one another along the x-direction.

Connection layer 108 may have a leveled top surface. For example, topsurfaces of second portions 108-2 of connection layer 108 may becoplanar with top surfaces of first portions 108-1 of connection layer108 along the z-direction. In some embodiments, the top surface ofconnection layer 108 (e.g., top surfaces of first portions 108-1 andsecond portions 108-2 of connection layer 108) may be higher than a topsurface of support structure 220 (or a top surface of cut structure114).

In some embodiments, connection layer 108 may include more than onesegment, each including at least one second portion 108-2 and aplurality of first portions 108-1 in contact with one another. Eachsegment may be over and in contact with one or more pairs of adjacentsource contacts 104 of the source structure. For example, the one ormore pairs of adjacent source contacts 104, connected to differentsegments of connection layer 108, may be separated by one or more sourcecontacts 104 that are not in contact with connection layer 108. Thespecific number of segments in connection layer 108 should be determinedbased on the design and/or fabrication of 3D memory device 100 andshould not be limited by the embodiments of the present disclosure. Insome embodiments, connection layer 108 may be over and in contact withall source contacts 104 in the respective source structure. A sourcevoltage may be applied on second portions 108-2 of the source structureso the all source contacts 104 connected to connection layer 108 can beapplied with the source voltage.

In some embodiments, a width of connection layer 108 (or its segments,if any) along the y-direction may vary, depending on the design and/orfabrication process of 3D memory device 100. In some embodiments,connection layer 108 may partially cover the source contacts 104underneath. That is, the width of connection layer 108 along they-direction is equal to or less than the width of the source structurealong the y-direction. In some embodiments, along the y-direction, thewidth of connection layer 108 is less than the width of the sourcestructure. In some embodiments, dielectric cap layer 115 may surroundconnection layer 108 along the x-direction so that connection layer 108is insulated from other devices or structures along various lateraldirections (e.g., along the x-y plane). Connection layer 108 may have auniformed width or varying width along the x-direction. For example,depending on the design and/or fabrication process, connection layer 108may have a “stripe” shape with uniformed width along the y-direction. Inanother example, different segments and/or portions of connection layer108 may have different widths along the y-direction. In someembodiments, conductive plugs (now shown, for applying a source voltageon connection layer 108) are formed on connection layer 108. In someembodiments, dielectric cap layer 115 may be partially located in blockregions 21. In some embodiments, dielectric cap layer 115 covers allchannel structures 110 in block region 21. Contact plugs (not shown) forconductively applying a drain voltage can subsequently be formedextending through dielectric cap layer 115 and form contact with channelstructures 110.

In some embodiments, cut structure 114 includes a suitable material thatis different from the sacrificial layers. During the gate replacementprocess to form conductor layers 123 and conductor portions 223, cutstructure 114 may retain from the etching of the sacrificial layers. Insome embodiments, cut structure 114 includes one or more of siliconoxide, silicon nitride, and/or silicon oxynitride. In some embodiments,conductor portions 223 may include the same material as conductor layers123 in adjacent block regions 21, and insulating portions 224 mayinclude the same material as insulating layers 124 in adjacent blockregions 21. For example, conductor portions 223 may include one or moreof tungsten, aluminum, cobalt, copper, polysilicon, and silicides, andinsulating portions 224 may include one or more of silicon oxide,silicon nitride, and silicon oxynitride. In some embodiments, connectionlayer 108 includes one or more of tungsten, aluminum, cobalt, copper,polysilicon, and silicides. In some embodiments, source contact 104includes polysilicon, and connection layer 108 includes tungsten. Insome embodiments, dielectric cap layer 115 includes silicon oxide. Insome embodiments, 3D memory device 100 includes an adhesion layer, e.g.,TiN, between source contact 104 and connection layer 108 to improve theadhesion and/or conductivity between source contact 104 and connectionlayer 108. In some embodiments, 3D memory device 100 includes anotheradhesion layer, e.g., TiN, between the respective insulating structureof source contact 104 and support structure 220 to improve the adhesionbetween the insulating structure and support structure 220.

3D memory device 100 can be part of a monolithic 3D memory device. Theterm “monolithic” means that the components (e.g., the peripheral deviceand memory array device) of the 3D memory device are formed on a singlesubstrate. For monolithic 3D memory devices, the fabrication encountersadditional restrictions due to the convolution of the peripheral deviceprocessing and the memory array device processing. For example, thefabrication of the memory array device (e.g., NAND channel structures)is constrained by the thermal budget associated with the peripheraldevices that have been formed or to be formed on the same substrate.

Alternatively, 3D memory device 100 can be part of a non-monolithic 3Dmemory device, in which components (e.g., the peripheral device andmemory array device) can be formed separately on different substratesand then bonded, for example, in a face-to-face manner. In someembodiments, the memory array device substrate (e.g., substrate 102)remains as the substrate of the bonded non-monolithic 3D memory device,and the peripheral device (e.g., including any suitable digital, analog,and/or mixed-signal peripheral circuits used for facilitating theoperation of 3D memory device 100, such as page buffers, decoders, andlatches; not shown) is flipped and faces down toward the memory arraydevice (e.g., NAND memory strings) for hybrid bonding. It is understoodthat in some embodiments, the memory array device substrate (e.g.,substrate 102) is flipped and faces down toward the peripheral device(not shown) for hybrid bonding, so that in the bonded non-monolithic 3Dmemory device, the memory array device is above the peripheral device.The memory array device substrate (e.g., substrate 102) can be a thinnedsubstrate (which is not the substrate of the bonded non-monolithic 3Dmemory device), and the back-end-of-line (BEOL) interconnects of thenon-monolithic 3D memory device can be formed on the backside of thethinned memory array device substrate.

FIG. 7A illustrates an exemplary pattern set 700 for forming the etchmasks used in the fabrication process. FIG. 7B illustrates an enlargedview of a unit 750 of the pattern set. Patterns in pattern set 700 maybe used in different stages of a fabrication process to form 3D memorydevice 100. In various embodiments, depending on the types ofphotoresist used in the patterning processes, patterns in pattern set700 may each be a part of an etch mask or a pattern for determining anetch mask. For example, if a negative photoresist is used forpatterning, the patterns in pattern set 700 may be used as parts of etchmasks; if a positive photoresist is used for patterning, the patterns inpattern set 700 may be complementary patterns for determining etchmasks. It should be noted that the shapes, dimensions, and ratios shownin FIGS. 7A and 7B are for illustrative purposes and are not to scale.

As shown in FIG. 7A, pattern set 700 includes patterns 702, 704, 706,and 708. Specifically, pattern 702 may be used for patterning slitopenings of a slit structure, pattern 704 may be used for patterningconnection layer 108, pattern 706 may be used for patterning cutstructure 114, and pattern 708 may be used for forming contact plugs incontact with and conductively connected to connection layer 108 and aperipheral circuit. Pattern set 700 may include a plurality of repeatingunits, e.g., 750, for the formation of cut structure 114, the slitopenings, and connection layer 108. The dimensions of patterns 702, 704,and 706 may be determined based on the fabrication processes and shouldnot be limited by the embodiments of the present disclosure.

FIG. 7B illustrates a repeating unit 750 that shows the details, e.g.,coverage, of each pattern. Depending on the fabrication process, if cutstructure 114 is used as an etch mask to form the slit openings, a widthW1 of pattern 706 along the y-direction may be equal to or greater thana width of the slit openings so that the subsequently-formed supportstructure 220 is in contact with block regions 21. If a separate etchmask, e.g., pattern 702 is used as an etch mask to form the slitopenings, width W1 of pattern 706 may be less than, equal to, or greaterthan width W2 of pattern 702; and a length D1 of pattern 706 may begreater than or equal to a length D2 between the two parts of pattern702 so that the two parts of pattern 702 can both overlap with pattern706 to ensure the slit openings and support structure 220 have desireddimensions in the x-y plane. A width W3 of pattern 704 may be less thanor equal to a width W1 of pattern 706 and width W2 of pattern 702 toensure connection layer 108 is effectively confined/insulated by thesubsequently-formed dielectric cap layer 115. A length D3 of pattern 704may be equal to or greater than length D2 and length D1, respectively,to ensure the material of dielectric cap layer 115 is completely removedover cut structure 114. In some embodiments, W3<W1<W2, and D2<D1<D3. Thesequence to apply the patterns may be described in the fabricationprocess for forming 3D memory device 100 below.

FIGS. 2-6 illustrate a fabrication process to form 3D memory device 100,and FIG. 9 illustrates a flowchart 900 of the fabrication process,according to some embodiments. For ease of illustration, FIGS. 7A and 7Bare illustrated together with FIGS. 2-6 to describe the fabricationprocess.

At the beginning of the process, at least one cut structure is formed ina stack structure (Operation 902). FIGS. 2A and 2B illustrate acorresponding structure 200.

As shown in FIGS. 2A and 2B, a cut structure 114 is formed in a stackstructure 111. Stack structure 111 may have a dielectric stack ofinterleaved initial sacrificial layers 133 i and initial insulatinglayers 134 i formed over a substrate 102. Initial sacrificial layers 133i may be used for subsequent formation of conductor layers 123. Initialinsulating layers 134 i may be used for subsequent formation ofinsulating layers 124. In some embodiments, stack structure 111 includesa first dielectric cap layer (not shown) on the top surface of stackstructure 111. 3D memory device 100 may include a channel region forforming channel structures 110. The channel region may include aplurality of source regions 22 and a block region 21 between adjacentsource regions 22.

Stack structure 111 may have a staircase structure. The staircasestructure can be formed by repetitively etching a material stack thatincludes a plurality of interleaved sacrificial material layers andinsulating material layers using an etch mask, e.g., a patterned PRlayer over the material stack. The interleaved sacrificial materiallayers and the insulating material layers can be formed by alternatinglydepositing layers of sacrificial material and layers of insulatingmaterial over substrate 102 until a desired number of layers is reached.The sacrificial material layers and insulating material layers can havethe same or different thicknesses. In some embodiments, a sacrificialmaterial layer and the underlying insulating material layer are referredto as a dielectric pair. In some embodiments, one or more dielectricpairs can form one level/staircase. During the formation of thestaircase structure, the PR layer is trimmed (e.g., etched incrementallyand inwardly from the boundary of the material stack, often from alldirections) and used as the etch mask for etching the exposed portion ofthe material stack. The amount of trimmed PR can be directly related(e.g., determinant) to the dimensions of the staircases. The trimming ofthe PR layer can be obtained using a suitable etch, e.g., an isotropicdry etch such as a wet etch. One or more PR layers can be formed andtrimmed consecutively for the formation of the staircase structure. Eachdielectric pair can be etched, after the trimming of the PR layer, usingsuitable etchants to remove a portion of both the sacrificial materiallayer and the underlying insulating material layer. The etchedsacrificial material layers and insulating material layers may forminitial sacrificial layers 133 i and initial insulating layers 134 i.The PR layer can then be removed.

The insulating material layers and sacrificial material layers may havedifferent etching selectivities during the subsequent gate-replacementprocess. In some embodiments, the insulating material layers and thesacrificial material layers include different materials. In someembodiments, the insulating material layers include silicon oxide, andthe deposition of insulating material layers include one or more ofchemical vapor deposition (CVD), atomic layer deposition (ALD), physicalvapor deposition (PVD), and sputtering. In some embodiments, thesacrificial material layers include silicon nitride, and the depositionof insulating material layers include one or more of CVD, PVD, ALD, andsputtering. In some embodiments, the etching of the sacrificial materiallayers and the insulating material layers include one or more suitableanisotropic etching process, e.g., dry etch.

A plurality of channel structures 110 can be formed in block region 21before or after the formation of cut structure 114. Channel structures110 may be formed before the formation of conductor layers 123. As anexample, channel structures 110 are formed before the formation of cutstructure 114. To form channel structures 110, a plurality of channelholes may be formed extending vertically through stack structure 111. Insome embodiments, a plurality of channel holes are formed through theinterleaved initial sacrificial layers 133 i and initial insulatinglayers 134 i. The plurality of channel holes may be formed by performingan anisotropic etching process, using an etch mask such as a patternedPR layer, to remove portions of stack structure 111 and expose substrate102. In some embodiments, at least one channel hole is formed on eachside of cut structure 114 along the y-direction. In some embodiments, aplurality of channel holes are formed in each block region 21. A recessregion may be formed at the bottom of each channel hole to expose a topportion of substrate 102 by the same etching process that forms thechannel hole above substrate 102 and/or by a separate recess etchingprocess. In some embodiments, a semiconductor plug is formed at thebottom of each channel hole, e.g., over the recess region. Thesemiconductor plug may be formed by an epitaxial growth process and/or adeposition process. In some embodiments, the semiconductor plug isformed by epitaxial growth and is referred to as the epitaxial portion.Optionally, a recess etch (e.g., dry etch and/or wet etch) may beperformed to remove excess semiconductor material on the sidewall of thechannel hole and/or control the top surface of the epitaxial portion ata desired position. In some embodiments, the top surface of theepitaxial portion is located between the top and bottom surfaces of thebottom initial insulating layer 134 i.

In some embodiments, the channel holes are formed by performing asuitable etching process, e.g., an anisotropic etching process (e.g.,dry etch) and/or an isotropic etching process (wet etch). In someembodiments, the epitaxial portion includes single crystalline siliconis formed by epitaxially grown from substrate 102. In some embodiments,the epitaxial portion includes polysilicon formed by a depositionprocess. The formation of epitaxially-grown epitaxial portion caninclude, but not limited to, vapor-phase epitaxy (VPE), liquid-phaseepitaxy (LPE), molecular-beam epitaxy (MPE), or any combinationsthereof. The formation of the deposited epitaxial portion may include,but not limited by, CVD, PVD, and/or ALD.

In some embodiments, a semiconductor channel is formed over and incontact with the epitaxial portion in the channel hole. Semiconductorchannel can include a channel-forming structure that has a memory film(e.g., including a blocking layer, a memory layer, and a tunnelinglayer), a semiconductor layer formed above and connecting the epitaxialportion, and a dielectric core filling up the rest of the channel hole.In some embodiments, memory film is first deposited to cover thesidewall of the channel hole and the top surface of the epitaxialportion, and a semiconductor layer is then deposited over memory filmand above epitaxial portion. The blocking layer, memory layer, andtunneling layer can be subsequently deposited in this order using one ormore thin film deposition processes, such as ALD, CVD, PVD, any othersuitable processes, or any combination thereof, to form memory film. Thesemiconductor layer can then be deposited on the tunneling layer usingone or more thin film deposition processes, such as ALD, CVD, PVD, anyother suitable processes, or any combination thereof. In someembodiments, a dielectric core is filled in the remaining space of thechannel hole by depositing dielectric materials after the deposition ofthe semiconductor layer, such as silicon oxide.

In some embodiments, a drain structure is formed in the upper portion ofeach channel hole. In some embodiments, parts of memory film,semiconductor layer, and dielectric core on the top surface of stackstructure 111 and in the upper portion of each channel hole can beremoved by CMP, grinding, wet etching, and/or dry etching to form arecess in the upper portion of the channel hole so that a top surface ofsemiconductor channel may be between the top surface and the bottomsurface of the first dielectric cap layer. The drain structure then canbe formed by depositing conductive materials, such as metals, into therecess by one or more thin film deposition processes, such as CVD, PVD,ALD, electroplating, electroless plating, or any combination thereof. Achannel structure 110 is thereby formed. A plurality of memory cells maysubsequently be formed by the intersection of the semiconductor channelsand the control conductor layers. Optionally, a planarization process,e.g., dry/wet etch and/or CMP, is performed to remove any excessmaterial on the top surface of stack structure 111.

One or more cut openings may be formed in source region 22, separatedfrom one another. Pattern 706 may be used for patterning the cutopenings. A depth of a cut opening may be equal to thickness t of cutstructure 114. In some embodiments, t is between the thicknesses of twoinitial sacrificial/insulating layer pairs and four initialsacrificial/insulating layer pairs. The value of t is determined basedon design and/or fabrication of 3D memory device 100 and should not belimited by the embodiments of the present disclosure. In someembodiments, an anisotropic etching process, such as dry etch, isperformed to remove a portion of stack structure 111 until a desiredthickness t is reached. In some embodiments, one or more selectiveetching processes are used to remove the portion of stack structure 111so the bottom surface of the cut opening can stop at a desired position(e.g., on a top surface of a desired initial insulating layer 134 i orinitial sacrificial layer 133 i) along the z-direction.

A suitable dielectric material, such as silicon oxide, is deposited tofill up the cut opening and form a respective cut structure 114. Asuitable deposition process, such as CVD, ALD, PVD, sputtering, or acombination thereof, can be performed to deposit the dielectricmaterial. In some embodiments, cut structure 114 is deposited by ALD.Optionally, a planarization process, e.g., CMP and/or recess etch, isperformed to remove any excess material over stack structure 111.

Referring back to FIG. 9, after the formation of the cut structures, apatterned cap material layer is formed over the one or more cutstructures, and an opening is formed over each cut structure (Operation904). FIGS. 3A-3C illustrate a corresponding structure 300.

As shown in FIGS. 3A and 3B, a patterned cap material layer 215 isformed in each source region 22, covering each cutting structure 114 inthe respective source region 22. An opening 214 may be formed over eachcut structure 114 in patterned cap material layer 215. Pattern 704 maybe employed for the formation of openings 214. Along the y-direction, awidth d1 of patterned cap material layer 215 may be greater than thedesired width of the subsequently-formed connection layer 108. In someembodiments, width d1 may be equal to or greater than the width of thesubsequently-formed source structure. A depth t1 of opening 214 may beless than or equal to a thickness of patterned cap material layer 215along the z-direction. In some embodiments, depth t1 is less than thethickness of patterned cap material layer 215 and patterned cap materiallayer 215 does not expose cut structure 114. In some embodiments, alongthe x-direction, a length l1 of opening 214 is greater than a length ofcut structure 114 (referring back to FIG. 7B and the description ofpatterns 704 and 706) so that opening 214 can fully cover cut structure114 along the x-direction. The dimensions of cut structure 114 andopening 214 can cause portions of patterned cap material layer 215 arecompletely removed along the x-direction in the space where connectionlayer 108 is formed. In some embodiments, along the y-direction, a widthd2 of opening 214 may be less than width d1 of patterned cap materiallayer 215.

Patterned cap material layer 215 may be formed by depositing a capmaterial layer to cover at least source regions 22 and perform apatterning process to remove portions of the cap material layer and formopenings 214. Any portions of the cap material layer outside of sourceregions 22 may be removed by the same patterning process or a differentpatterning process. The cap material layer can be deposited by one ormore of CVD, ALD, PVD, sputtering, or a combination thereof. In someembodiments, the patterning process includes a photolithography process(e.g., using pattern 704) and an etching process, e.g., dry and/or wetetch. The time for etching opening 214 may be controlled so depth t1 canreach a desired value.

Referring back to FIG. 9, after the formation of the patterned capmaterial layer, portions of the stack structure and the patterned capmaterial layer are removed to form a slit structure, at least oneinitial support structure, and a cap layer (Operation 906). The at leastone initial support structure, dividing the slit structure into aplurality of slit openings, each has a cut structure and interleaved aplurality of sacrificial portions and a plurality of insulating portionsunderneath the cut structure. FIGS. 4A and 4B illustrate a correspondingstructure 400.

As shown in FIGS. 4A and 4B, portions of stack structure 111 andpatterned cap material layer 215 in source region 22, adjacent to eachopening 214, are removed to form a slit structure 106, which exposessubstrate 102. Dielectric cap layer 115 may be formed extending alongthe x-direction from the etching of patterned cap material layer 215.Dielectric cap layer 115 may surround slit structure 106 on both sidesalong the y-direction. In some embodiments, a top surface of dielectriccap layer 115 may be higher than the top surfaces of support structures220 along the z-direction. In some embodiments, along the z-x plane, asidewall of dielectric cap layer 115 may be coplanar with a sidewall ofthe respective slit opening. Pattern 702 may be used for patterning slitstructure 106 and dielectric cap layer 115. That is, portions of stackstructure 111 and patterned cap material layer 215, in source region 22and adjacent to cut structure 114, are removed to form slit structure106 such that opening 214 is in contact with adjacent slit openingsalong the x-direction. Cut structure 114 and the underneath interleavedsacrificial portions and insulating portions 224 (e.g., remainingportions of initial sacrificial layer 133 i and initial insulating layer134 i after the etching of slit structure 106) may form an initialsupport structure. The sacrificial portions and insulating portions 224may each be in contact with the sacrificial layers and insulating layers124 of the same level in adjacent block regions 21. In some embodiments,cut structure 114 may also include any remaining portion of patternedcap material layer 215 on cut structure 114. The one or more initialsupport structures may divide slit structure 106 into a plurality ofslit openings, each exposing substrate 102 and interleaved sacrificiallayers and insulating layers of adjacent block regions 21. Depending onthe fabrication process, along the y-direction, the width of cutstructure 114 may be less than, equal to, or greater than the width ofslit structure 106. A suitable anisotropic etching process, e.g., dryetch, can be performed to form slit structure 106.

Referring back to FIG. 9, after the formation of the slit structures andthe initial support structures, the sacrificial portions in each initialsupport structure and the sacrificial layers in each block region arereplaced with conductor portions and conductor layers, forming at leastone support structure and a plurality of memory blocks (Operation 908).FIGS. 4A and 4B illustrate the corresponding structure 400.

As shown in FIGS. 4A and 4B, the sacrificial portions in each initialsupport structure are replaced with a plurality of conductor portions223. The sacrificial layers in each block region 21 are replaced with aplurality of conductor layers 123 (referring back to FIG. 1C). Anisotropic etching process, e.g., wet etch, can be performed to removethe sacrificial portions and sacrificial layers through slit structures106. A plurality of lateral recesses may be formed in each block region21 by the removal of the sacrificial layers, and a plurality of recessportions may be formed in each initial support structure by the removalof the sacrificial portions. A conductor material may then be depositedto fill up the lateral recesses and recess portions, forming theplurality of conductor layers 123 in each block region and the pluralityof conductor portions 223 in each initial support structure.Accordingly, portion stack 221, having a plurality of interleavedconductor portions 223 and insulating portions 224, may be formed.Support structure 220, having cut structure 114 and portion stack 221underneath, may be formed. Optionally, a spacer layer 225 is formed tosurround interleaved conductor portions 223 and insulating portions 224,further isolating conductor portions 223 from the subsequently-formedsource structure. In some embodiments, when spacer layer 225 is notformed, the insulating structures of source contacts 104 provideelectrical insulation between source contacts 104 and conductor portions223. In some embodiments, the conductor material and spacer layer 225 iseach deposited by at least one of CVD, PVD, ALD, and sputtering.

Referring back to FIG. 9, after the formation of the support structureand conductor layers, a source structure is formed in the slit structure(Operation 910). FIGS. 5A and 5B illustrate a corresponding structure500.

As shown in FIGS. 5A and 5B, a source structure is formed in slitstructure 106. The source structure may include an insulating structurein each slit opening of slit structure 106 and a source contact 104 ineach insulating structure. A top surface of each source contact 104 maybe lower than the top surface of support structure 220 (or cut structure114). In some embodiments, top surfaces of source contacts 104 may becoplanar with one another, and may be located between the top and thebottom surfaces of cut structure 114. Optionally, an adhesion layer (notshown) is deposited over the top surface and/or sidewalls of supportstructure 220 before the formation of the source structure. In someembodiments, the insulating structure includes silicon oxide and sourcecontacts 104 include polysilicon. The insulating structure and sourcecontacts 104 may each be deposited by one or more of CVD, PVD, ALD, andsputtering. A recess etching process may be performed on the insulatingstructure to expose substrate 102 such that the respective sourcecontact 104 can be in contact with substrate 102. Optionally, a recessetching process, dry and/or wet etch, is performed to remove the excessmaterial of source contact 104, e.g., to ensure desired verticalpositions of the top surfaces of source contacts 104, before thedeposition of the adhesion layer. In some embodiments, the adhesionlayer includes TiN and is deposited by one or more of CVD, PVD, ALD,electroplating, and sputtering. In some embodiments, top surfaces ofsource contacts 104 may be lower than a top surface of support structure220 (or cut structure 114 in this operation). Optionally, a recessetching process may be performed to etch back source contacts 104 toform sufficient space in slit structure 106 for the formation ofconnection layer 108.

Referring back to FIG. 9, after the formation of the source structure,the space formed by the rest of the slit structure and the dielectriccap layer is filled with a conductive material to form a connectionlayer (Operation 912). FIGS. 6A and 6B illustrate a correspondingstructure 600.

As shown in FIGS. 6A-6C, in source region 22, the space formed by therest of slit structure 106 (e.g., the portion of slit structure notfilled with source contacts 104 and insulating structures) anddielectric cap layer 115, may be filled with a suitable conductivematerial, forming connection layer 108. The space may have a“trench-like” shape, and may include the portion of slit structure 106over the source structure and the space formed by the surrounding ofdielectric cap layer 115. For example, along the z-x plane, thesidewalls of dielectric cap layer 115 and sidewalls of the slit openingsnot in contact with the respective source structure may form a pair ofsidewalls of the space along the z-x plane. In some embodiments,dielectric cap layer 115 also covers at least a portion of block region21. In some embodiments, dielectric cap layer 115 covers all channelstructures 110 in block region 21. The bottom surfaces of the rest ofslit structure 106 (e.g., the top surfaces of source structure and cutstructure 114) may form the bottom surfaces of the space. The conductivematerial may be deposited on at least a pair of adjacent source contacts104 and the support structure 220 between any pair of adjacent sourcecontacts 104. In some embodiments, the conductive material is depositedto fill up the space in the entire source region 22 so connection layer108 is in contact with all source contacts 104 and support structures220 in source region 22. The portion of connection layer 108 over sourcecontact 104 may be referred to as first portion 108-1 of connectionlayer 108, and the portion of connection layer 108 over supportstructure 220 may be referred to as second portion 108-2 of connectionlayer 108. Second portion 108-2 of connection layer 108 may be incontact with adjacent first portions 108-1 of connection layer 108 alongthe x-direction. Optionally, an adhesion layer (not shown) is depositedover the top surface of source contacts 104 before the formation ofconnection layer 108.

In some embodiments, the conductive material includes one or more oftungsten, aluminum, copper, cobalt, polysilicon, and silicides. Theconductive material and any adhesion layer may be deposited by one ormore of CVD, PVD, ALD, sputtering, and/or electroplating. In someembodiments, source contacts 104 includes polysilicon and connectionlayer 108 include tungsten. Optionally, a planarization process, e.g.,CMP and/or recess etch, is performed to remove any excess material overconnection layer 108. In some embodiments, the top surfaces of firstportions 108-1 and second portions 108-2 of connection layer 108 may becoplanar in the x-y plane. In some embodiments, the top surface ofconnection layer 108 (e.g., including the top surfaces of first portions108-1 and second portions 108-2 of connection layer 108) may be coplanarwith the top surface of respective dielectric cap layer 115. In someembodiments, the top surface of connection layer 108 is higher than thetop surfaces of support structures 220 along the z-direction.

In some embodiments, a 3D memory device includes a memory stack, aplurality of channel structures, and a source structure. The memorystack is over a substrate and includes interleaved a plurality ofconductor layers and a plurality of insulating layers. The plurality ofchannel structures extend vertically in the memory stack. The sourcestructure extend in the memory stack. The source structure includes aplurality of source contacts each in a respective insulating structure,and two adjacent ones of the plurality of source contacts areconductively connected to one another by a connection layer. A pair offirst portions of the connection layer are over the two adjacent ones ofthe plurality of source contacts and a second portion of the connectionlayer being between the two adjacent ones of the plurality of sourcecontacts. Top surfaces of the pair of first portions of the connectionare coplanar with a top surface of the second portion of the connectionlayer.

In some embodiments, the connection layer includes at least one oftungsten, cobalt, aluminum, copper, silicides, or polysilicon.

In some embodiments, the connection layer is over and in contact witheach of the plurality of source contacts.

In some embodiments, the 3D memory device further includes a cap layersurrounding the connection layer along a lateral direction along whichthe connection layer extends.

In some embodiments, along a lateral direction perpendicular to thelateral direction along which the connection layer extends, a width ofthe connection layer is equal to or less than a width of the sourcestructure.

In some embodiments, the source structure further includes a supportstructure between the two adjacent ones of the plurality of sourcecontacts and covered by the second portion of the connection layer, thesupport structure being in contact with memory blocks adjacent to thesource structure.

In some embodiments, the top surfaces of the pair of first portions andthe second portion of the connection layer are higher than a top surfaceof the support structure along a vertical direction.

In some embodiments, the support structure includes a cut structure overinterleaved a plurality of conductor portions and a plurality ofinsulating portions. Each of the plurality of conductor portions may bein contact with corresponding conductor layers in the memory blocksadjacent to the source structure. Each of the plurality of insulatingportions may be in contact with corresponding insulating layers in thememory blocks adjacent to the source structure.

In some embodiments, the support structure includes a spacer layer incontact with and surrounding the interleaved plurality of conductorportions and insulating portions.

In some embodiments, the cut structure includes silicon oxide.

In some embodiments, a thickness of the cut structure is betweeninterleaved two conductor layers and two insulating layers andinterleaved four conductor layers and four insulating layers. In someembodiments, along a lateral direction perpendicular to the lateraldirection along which the connection layer extends, a width of the cutstructure is equal to or less than a width of the source structure.

In some embodiments, the plurality of source contacts include at leastone of cobalt, aluminum, copper, silicides, or polysilicon.

In some embodiments, the 3D memory device further includes an adhesionlayer between insulating structures of the two adjacent ones of theplurality of source contacts and the support structure, and between thetwo adjacent ones of the plurality of source contacts and the connectionlayer.

In some embodiments, the adhesion layer includes titanium nitride.

In some embodiments, the plurality of channel structures each includesan epitaxial portion in contact with and conductively connected to thesubstrate, a semiconductor channel in contact with and conductivelyconnected to the epitaxial portion, and a drain structure in contactwith and conductively connected to the semiconductor channel.

In some embodiments, a 3D memory device includes a memory stack, aplurality channel structures, and a plurality of source structures. Thememory stack is over a substrate. The memory stack includes interleaveda plurality of conductor layers and a plurality of insulating layers.The plurality of channel structures extend vertically in the memorystack. The plurality of source structures extend in parallel along alateral direction in the memory stack. The plurality of sourcestructures each includes a plurality of source contacts each in arespective insulating structure, a plurality of support structures eachin contact with adjacent insulating structures along the lateraldirection, and a connection layer conductively connected to at least twoadjacent ones of the plurality of source contacts. The connection layerinclude at least two first portions over the at least two adjacent onesof the plurality of source contacts and at least one second portionbetween the at least two adjacent ones of the plurality of sourcecontacts Top surfaces of the at least two first portions and the atleast one second portion of the connection layer are coplanar with oneanother.

In some embodiments, the connection layer includes at least one oftungsten, cobalt, aluminum, copper, silicides, or polysilicon.

In some embodiments, the connection layer is over and in contact witheach of the plurality of respective source contacts.

In some embodiments, the 3D memory device further includes a cap layersurrounding the connection layer along a lateral direction along whichthe connection layer extends.

In some embodiments, along another lateral direction perpendicular tothe lateral direction along which the connection layer extends, a widthof the connection layer is equal to or less than a width of therespective source structure.

In some embodiments, the plurality of support structures each includes acut structure over interleaved a plurality of conductor portions and aplurality of insulating portions. Each of the plurality of conductorportions may be in contact with corresponding conductor layers in thememory blocks adjacent to the respective source structure. Each of theplurality of insulating portions may be in contact with correspondinginsulating layers in the memory blocks adjacent to the respective sourcestructure.

In some embodiments, the top surfaces of the at least two first portionsand the at least one second portion of the connection layer are higherthan top surfaces of the plurality of support structures along avertical direction.

In some embodiments, the cut structure includes silicon oxide.

In some embodiments, a thickness of the cut structure is betweeninterleaved two conductor layers and two insulating layers andinterleaved four conductor layers and four insulating layers. In someembodiments, along a lateral direction perpendicular to the lateraldirection along which the respective connection layer extends, a widthof the cut structure is equal to or less than a width of the respectivesource structure.

In some embodiments, the plurality of source contacts include at leastone of cobalt, aluminum, copper, silicides, or polysilicon.

In some embodiments, the 3D memory device further includes an adhesionlayer between the at least two adjacent ones of the plurality of sourcecontacts and the connection layer and between the at least two adjacentones of the plurality of source contacts and the support structure.

In some embodiments, the adhesion layer includes titanium nitride.

In some embodiments, the plurality of channel structures each includesan epitaxial portion in contact with and conductively connected to thesubstrate, a semiconductor channel in contact with and conductivelyconnected to the epitaxial portion, and a drain structure in contactwith and conductively connected to the semiconductor channel.

In some embodiments, a method for forming a 3D memory device includesthe following operations. A cut structure is first formed in a stackstructure. The stack structure includes interleaved a plurality ofinitial sacrificial layers and a plurality of initial insulating layers.A patterned cap material layer is formed over the stack structure. Thepatterned cap material layer includes an opening over the cut structure.Portions of the stack structure and the patterned cap material layeradjacent to the opening are removed to form a slit structure and aninitial support structure. The initial support structure divide the slitstructure into a plurality of slit openings. A plurality of conductorportions are formed through the plurality of slit openings to form asupport structure. A source contact is formed in each of the pluralityof slit openings. A connection layer is formed over the source contactin each of the plurality of slit openings and over the supportstructure.

In some embodiments, forming the cut structure includes patterning thestack structure to form a cut opening in a source region and depositinga dielectric material to fill up the cut opening.

In some embodiments, forming the patterned cap material layer includesdepositing a cap material layer to cover the source region and removinga portion of the cap material layer to form the opening over the cutstructure.

In some embodiments, removing portions of the stack structure and thepatterned cap material layer adjacent to the opening includes removingportions of the stack structure and the patterned cap material layer inthe source region and adjacent to the cut structure and the opening,such that the opening is in contact with adjacent slit openings, each ofthe plurality of slit openings exposes the substrate, the cut structureand interleaved a plurality of sacrificial portions and a plurality ofinsulating portions form the initial support structure, and a cap layeris formed surrounding the slit structure along a lateral direction inwhich the slit structure extends.

In some embodiments, forming the plurality of conductor portionsincludes removing, through the plurality of slit openings, the pluralityof sacrificial portions in the initial support structure to form aplurality recess portions. In some embodiments, forming the plurality ofconductor portions also includes depositing a conductor material to fillup the plurality of recess portions to form the plurality of conductorportions, the initial support structure forming a support structure.

In some embodiments, the method further includes forming a plurality ofconductor layers in a plurality of block portions of the stack structurein the same operations that form the plurality of conductor portions,such that the plurality of block portions is in contact with the initialsupport structure. The plurality of conductor layers may be formed byremoving, through the plurality of slit openings, a plurality ofsacrificial layers in the plurality of block portions to form aplurality of lateral recesses, and depositing the conductor material tofill up the plurality of lateral recesses to form the plurality ofconductor layers.

In some embodiments, forming the source contact includes depositing atleast one of cobalt, aluminum, copper, silicides, or polysilicon intothe respective slit opening, such that a top surface of the sourcecontact is lower than a top surface of the support structure along thevertical direction.

In some embodiments, forming the connection layer includes depositing atleast one of tungsten, cobalt, aluminum, copper, silicides, orpolysilicon to fill up a space formed by a portion of the slit structurenot filled with the source structure and the cap layer.

In some embodiments, the method further includes depositing an adhesionlayer between in each of the plurality of slit openings and forming aninsulating structure in the slit opening before forming the sourcecontact.

The foregoing description of the specific embodiments will so reveal thegeneral nature of the present disclosure that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent disclosure. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

Embodiments of the present disclosure have been described above with theaid of functional building blocks illustrating the implementation ofspecified functions and relationships thereof. The boundaries of thesefunctional building blocks have been arbitrarily defined herein for theconvenience of the description. Alternate boundaries can be defined solong as the specified functions and relationships thereof areappropriately performed.

The Summary and Abstract sections may set forth one or more but not allexemplary embodiments of the present disclosure as contemplated by theinventor(s), and thus, are not intended to limit the present disclosureand the appended claims in any way.

The breadth and scope of the present disclosure should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. A three-dimensional (3D) memory device,comprising: a memory stack over a substrate, the memory stack comprisinginterleaved a plurality of conductor layers and a plurality ofinsulating layers; a plurality of channel structures extendingvertically in the memory stack; and a source structure extending in thememory stack, wherein the source structure comprises a plurality ofsource contacts each in a respective insulating structure, and twoadjacent ones of the plurality of source contacts are conductivelyconnected to one another by a connection layer, a pair of first portionsof the connection layer being over the two adjacent ones of theplurality of source contacts and a second portion of the connectionlayer being between the two adjacent ones of the plurality of sourcecontacts, and top surfaces of the pair of first portions of theconnection being coplanar with a top surface of the second portion ofthe connection layer.
 2. The 3D memory device of claim 1, wherein theconnection layer comprises at least one of tungsten, cobalt, aluminum,copper, silicides, or polysilicon.
 3. The 3D memory device of claim 1,wherein the connection layer is over and in contact with each of theplurality of source contacts.
 4. The 3D memory device of claim 3,further comprising a cap layer surrounding the connection layer along alateral direction along which the connection layer extends.
 5. The 3Dmemory device of claim 4, wherein along a lateral directionperpendicular to the lateral direction along which the connection layerextends, a width of the connection layer is equal to or less than awidth of the source structure.
 6. The 3D memory device of claim 1,wherein the source structure further comprises a support structurebetween the two adjacent ones of the plurality of source contacts andcovered by the second portion of the connection layer, the supportstructure being in contact with memory blocks adjacent to the sourcestructure.
 7. The 3D memory device of claim 6, wherein the top surfacesof the pair of first portions and the second portion of the connectionlayer are higher than a top surface of the support structure along avertical direction.
 8. The 3D memory device of claim 7, wherein thesupport structure comprises a cut structure over interleaved a pluralityof conductor portions and a plurality of insulating portions, each ofthe plurality of conductor portions being in contact with correspondingconductor layers in the memory blocks adjacent to the source structure,and each of the plurality of insulating portions being in contact withcorresponding insulating layers in the memory blocks adjacent to thesource structure.
 9. The 3D memory device of claim 8, wherein the cutstructure comprises silicon oxide.
 10. A three-dimensional (3D) memorydevice, comprising: a memory stack over a substrate, the memory stackcomprising interleaved a plurality of conductor layers and a pluralityof insulating layers; a plurality of channel structures extendingvertically in the memory stack; and a plurality of source structuresextending in parallel along a lateral direction in the memory stack,wherein the plurality of source structures each comprises: a pluralityof source contacts each in a respective insulating structure, aplurality of support structures each in contact with adjacent insulatingstructures along the lateral direction, and a connection layerconductively connected to at least two adjacent ones of the plurality ofsource contacts, the connection layer comprising at least two firstportions over the at least two adjacent ones of the plurality of sourcecontacts and at least one second portion between the at least twoadjacent ones of the plurality of source contacts, and top surfaces ofthe at least two first portions and the at least one second portion ofthe connection layer being coplanar with one another.
 11. The 3D memorydevice of claim 10, wherein the connection layer comprises at least oneof tungsten, cobalt, aluminum, copper, silicides, or polysilicon. 12.The 3D memory device of claim 10, wherein the connection layer is overand in contact with each of the plurality of respective source contacts.13. The 3D memory device of claim 12, wherein along another lateraldirection perpendicular to the lateral direction along which theconnection layer extends, a width of the connection layer is equal to orless than a width of the respective source structure.
 14. The 3D memorydevice of claim 10, wherein the plurality of support structures eachcomprises a cut structure over interleaved a plurality of conductorportions and a plurality of insulating portions, each of the pluralityof conductor portions being in contact with corresponding conductorlayers in the memory blocks adjacent to the respective source structure,each of the plurality of insulating portions being in contact withcorresponding insulating layers in the memory blocks adjacent to therespective source structure.
 15. The 3D memory device of claim 14,wherein the top surfaces of the at least two first portions and the atleast one second portion of the connection layer are higher than topsurfaces of the plurality of support structures along a verticaldirection.
 16. A method for forming a three-dimensional (3D) memorydevice, comprising: forming a cut structure in a stack structure, thestack structure comprising interleaved a plurality of initialsacrificial layers and a plurality of initial insulating layers; forminga patterned cap material layer over the stack structure, the patternedcap material layer comprising an opening over the cut structure;removing portions of the stack structure and the patterned cap materiallayer adjacent to the opening to form a slit structure and an initialsupport structure, the initial support structure dividing the slitstructure into a plurality of slit openings; forming a plurality ofconductor portions through the plurality of slit openings to form asupport structure; forming a source contact in each of the plurality ofslit openings; and forming a connection layer over the source contact ineach of the plurality of slit openings and over the support structure.17. The method of claim 16, wherein forming the patterned cap materiallayer comprises: depositing a cap material layer to cover the sourceregion; and removing a portion of the cap material layer to form theopening over the cut structure.
 18. The method of claim 17, whereinremoving portions of the stack structure and the patterned cap materiallayer adjacent to the opening comprises removing portions of the stackstructure and the patterned cap material layer in the source region andadjacent to the cut structure and the opening, such that: the opening isin contact with adjacent slit openings; each of the plurality of slitopenings exposes the substrate; the cut structure and interleaved aplurality of sacrificial portions and a plurality of insulating portionsform the initial support structure; and a cap layer is formedsurrounding the slit structure along a lateral direction in which theslit structure extends.
 19. The method of claim 16, wherein forming theplurality of conductor portions comprises: removing, through theplurality of slit openings, the plurality of sacrificial portions in theinitial support structure to form a plurality recess portions; anddepositing a conductor material to fill up the plurality of recessportions to form the plurality of conductor portions, the initialsupport structure forming a support structure.
 20. The method of claim19, wherein forming the source contact comprises depositing at least oneof cobalt, aluminum, copper, silicides, or polysilicon into therespective slit opening, such that a top surface of the source contactis lower than a top surface of the support structure along the verticaldirection; and forming the connection layer comprises depositing atleast one of tungsten, cobalt, aluminum, copper, silicides, orpolysilicon to fill up a space formed by a portion of the slit structurenot filled with the source structure and the cap layer.